This paper proposes a personal network approach to the study of structural assimilation and structural transnationalism among international immigrants. Structural assimilation and transnationalism are defined as embeddedness in native social networks of the host society, and in co-national social networks of the origin society, respectively. Data on the personal networks of international immigrants, each including 45 alters, are obtained from two surveys among Moroccan, Senegalese and Gambian immigrants in Spain (N = 139), and among Sri Lankan immigrants in Italy (N = 102). Measures on the size of different national and geographical classes of alters, and on the cohesion within and between these classes, are used to quantify the degree and type of structural assimilation and transnationalism. Linear regression models show that these measures are significantly associated with outcomes of cultural and economic assimilation of immigrants.